RAT,
I read that Bob Woodfill article in Muzzle Blasts on the Bridger rifle where he thought that Bridger acquired the rifle at Ft. Laramie around 1865 before leaving for his trip in 1866 scouting a trail to Virginia City Montana. As a result, Woodfill attributed the Jim Bridger Hawken in the MHS collection to J.P. Gemmer.
That struck me as odd. I had never seen anyone else make that attribution.
John Baird has J.P. Gemmer joining the Union Army during the Civil War and working at the Government Arsenal in St. Louis as a gunsmith. I haven't seen any other writers provide details on Gemmer's military service, but it should be easy to verify in Army records. Baird has Gemmer taking over the Hawken shop after the Civil War ended.
The business directories and advertisements in the local newspapers have William L. Watt - Successor to W. S. Hawken in 1860 (Baird, pgs 16 and 70) and Watt is still listed as the proprietor in 1864 (Hanson, pg 44). Gemmer is listed as a gunsmith at the Hawken shop address, 21 Washington Av., in Edward's 1865 directory (Hanson, pg 44). Gemmer isn't listed as proprietor of the shop until 1866 (Baird, pg 16). This all fits with Gemmer being in the Army during the war.
That doesn't give Gemmer much time to make all the patterns and molds for the cast parts on the Bridger Hawken, make the rifle, and for the rifle to have been transported all the way to the mountains in time for Bridger to buy it in 1865.
I was in Santa Fe for a few days last December studying the guns in Jim Gordon's museum and an afternoon at the Masonic Lodge studying, measuring, and photographing the Kit Carson Hawken. The quality of the several Gemmer marked guns in Gordon's collection (they are also pictured in Gordon's books) was way below the quality I saw in the Carson Hawken. (I haven't seen the Bridger Hawken in person in decades, but from the pictures, it looks close to the Carson Hawken.)
It's hard for me to understand how and why Gemmer would put so much excellent workmanship in rifles he marked with "S. HAWKEN", if he made the Carson and Bridger rifles, and settle for a much lower level of workmanship in rifles he marked with his own name. I don't think he did.
The Carson Hawken (and the several other S. Hawken rifles that are similar) is the apex of the evolutionary development of the Hawken rifle. It's nearly perfect in its design and execution. Probably something Sam was working towards his whole career.
Whatever you choose to call it, you built a very fine rifle.